One of them is this:
When we feel Anger, Eckhart teach we have to be the witness of anger to avoid to be identify with it. If a situation make grow anger inside me, I'm able to be the witness of the Anger energy, but after, what I have to do ? Because, yes, I'm the witness of anger, but the energy want to get out of my body. The energy want to express itself by the language or by hitting something like a pillow.

Are we supposed to express the anger by doing what the energy want to do ? (express the anger by talking or hitting a pillow). In other word, do we have to be the witness of anger and in same time to express it without to be identify with this energy ?

The point of being a witness to the anger is to recognize that you are not the anger. The anger is something you feel, an energy within you, but it is not you. In the practice of observing any and all of our feeling states we get a better sense of our own natural being as distinct from the conditional energy we feel in the many challenging ways that life unfolds. The goal is to be clear on who we are and that it is not the emotions flowing within our consciousness.

I suggest an approach to anger, or any emotion that we do not like, is to understand how that emotion came to be. To start with, one must recognize that it has less to do with the external conditions we perceive and more to do with the context in which we see them. If we are angry, it's because we are seeing the circumstance of our emotion in the limited context of our ingrained belief system. Ask yourself what does the conditions of your anger mean to you that it makes you angry. Somewhere within you there is a belief that holds a certain meaning that triggers your anger.

You can beat the pillow all day long and, while it may channel some emotional energy away through physical exertion, it won't change the underlying cause for your experience. That underlying cause is based in the meaning you believe applies to the conditions you dislike. Change the meaning you apply to those same conditions and you will change the experience of them you have.

Another look at the nature of anger is how it mis-aligns with your greater being. In these human forms we are but extensions of a far greater being that is our true nature. That extension that is us exists for the purpose of exploring unique conditions for the valuable experience they offer. It all goes toward the evolution of our greater consciousness and being. That greater being is infinitely loving and free of judgment and condemnation.

Our moments of anger, as well as all other negative emotions, are in direct contrast to the infinitely loving nature of our true beingness. In that, those negative emotions are a gift of sorts as they are clear messages that we are perceiving things in a way that is different from our infinitely loving true nature. Pain is the contrast that distinguishes clarity from the meaning held in our distorted beliefs.

There is nothing wrong here. It is simply how a wonderful system of life experience and being works. Learn the rules that govern the system and you can make them work to your lasting benefit. Think in ways that releases negative energy. Make a practice of meditation or some other method of aligning with your inner being, your true nature. That alignment is key to the guidance that will help you through all of life's challenges. That alignment will help you create new meanings for the conditions of your life that will not give rise to anger, but instead foster inclusion. And that inclusion is the essence of the evolution of consciousness in this human form.

Who is it that that holds this anger energy? Who is it that needs to express it? Observe this energy more closely, become intimate with it, eat it and understand it. Heavy emotions suffocate from our attention.